Why gymnosperms

The evolution of the seed marks one of the most important innovations in the history of land plants, leading to enhanced survival and dispersal capabilities and to greater mating control.   Seed plants have come to dominate the landscape and today, forests and grasslands are among our most important resources.   Additionally, the stage was set for the origin of agriculture, based on the cultivation of grain (seed)-bearing plants, which provide the majority of the calories consumed by humans and the animals that feed them. 

Extant seed plants number approximately 300,000 species, far more than all other land plants combined (~35,000).   Within seed plants there is further numerical disparity.   The majority are flowering plants (angiosperms), with just under 1,100 species being distributed among the gymnosperm clades: cycads (300), ginkgos (1), Gnetales (90), and conifers (700).   These clades are a relict of seed plant diversity, representing just 20% of the major taxa that are known from the fossil record.

Current hypotheses of seed plant relationships remain controversial, and the problem has the hallmarks typical of other difficult phylogenetic questions: the disparity in the size of clades, the pruning of taxa from the tree through extinction, and extreme variation in rates of nucleotide substitution among clades that are anciently diverged.   This leaves a series of important questions unanswered, including the question of what are the steps that led to the origin and remarkable radiation of the angiosperms. 

With funding through NSF's Assembling the Tree of Life (AToL) program, we are working to meet the following objectives.